CN105460006B - Vehicle with a steering wheel - Google Patents

Abstract

Disclosed is a vehicle, a hybrid electric vehicle including: an engine that can selectively provide a drive torque to propel the vehicle; an electric motor also selectively provides drive torque. The differential transfers torque to and between the wheels. The planetary gear set is coupled to the engine and has a ring gear that transmits ring gear torque to a differential. A continuous torque transmitting member operatively couples the ring gear and the electric machine to the differential. At least one controller configured to vary engine output based on a ring gear torque threshold. This enables the desired torque to be transmitted to the differential through the continuous torque transmitting member.

Description

vehicle

technical field

The present disclosure relates to altering engine torque in a hybrid vehicle to manage torque transmitted through a ring gear coupled to planetary gears of the engine.

Background technique

Hybrid vehicles are typically driven by two primary power sources (for example, an internal combustion engine and an electric motor (powered by a battery). One type of hybrid vehicle is a power-split hybrid vehicle. A power-split hybrid allows the engine and The electric motor supplies power to the wheels individually or in combination. A planetary gear set can be combined to the engine and generator so that the engine can charge the battery even when the electric motor is providing the necessary torque to propel the vehicle. The generator can also be supplied by The torque from the planetary gear set acts as an electric motor. One of the planetary gears (eg, a ring gear) may also combine the engine and generator to an output (such as a differential that distributes torque to the wheels).

Particularly at low vehicle speeds, situations may arise where the amount of wheel power may be very small despite the relatively large wheel torque demand. The most extreme case of this is when the vehicle starts from a standstill with full accelerator pedal (when wheel speed is zero (and therefore wheel power)), but the wheel torque demand is at its maximum. Another similar situation may arise where the vehicle operator presses the accelerator pedal sharply while the vehicle is running at low or zero speed over sand or gravel. In these and other similar situations, at normal battery state of charge (SOC), the desired engine power produced corresponds to the power necessary to overcome losses in transmission and accessory loads.

Hybrid vehicle structures should be designed to appropriately accommodate such driving conditions while also providing expected torque to the wheels to propel the vehicle. In one type of power split hybrid, a series of reduction gears transfer torque from a planetary gear set to a differential that distributes torque among the wheels. For example, in one vehicle, the engine may be connected to the carrier of the planetary gear set, while the sun gear is connected to the generator. The torque output by the engine causes the sun gear to rotate, which turns the generator to charge the battery or provide drive torque through the traction motor. In addition, the ring gear of the planetary gear set turns a series of torque reduction gears that ultimately turn the output of the traction motor and driveline. There are control strategies for delivering optimal torque to the wheels based on the amount of torque delivered through the ring gear during the low speed and high torque conditions described above. However, these control strategies account for a series of reduction gears when determining how much torque the engine and/or electric motor produces.

In another type of power split hybrid vehicle, a chain, belt or other continuous torque transmitting member transfers torque from the planetary gear set to the differential. No reducer is set.

SUMMARY OF THE INVENTION

According to one embodiment, a vehicle includes an engine, a planetary gear set, a differential, an electric machine, a continuous torque transfer component, and at least one controller. A planetary gear set is coupled to the engine and has a ring gear that transmits ring gear torque to the differential. The electric machine is configured to selectively output torque to the differential. A continuous torque transmitting component (CTTM) operably couples the ring gear and electric motor to the differential. The controller is configured to vary the engine output based on the ring gear torque threshold such that the desired torque is transmitted to the differential through the CTTM.

At least one controller may be configured to increase the engine output to maintain the ring gear torque above the ring gear torque threshold to transfer the desired torque to the differential through the CTTM.

Active components, such as gears or sprockets, may be coupled to the CTTM to provide torque to the CTTM. The active member may have a central shaft operatively coupled to the ring gear at one end and to the motor at the other end.

According to another embodiment, a method of controlling an engine output of a vehicle is provided. The vehicle includes an engine operably coupled to a differential through a ring gear in a planetary gear set and a continuous torque transfer member (CTTM). The vehicle also has an electric machine operably coupled to the differential via CTTM. The method includes increasing engine output based on the amount of torque transmitted through the ring gear such that the torque remains above a ring gear torque threshold and transmitting the torque through the CTTM.

According to one embodiment of the present disclosure, wherein increasing the engine output includes increasing a minimum engine power threshold.

According to one embodiment of the present disclosure, the method further includes maintaining engine output above a minimum engine power threshold such that torque transmitted through the ring gear remains above the ring gear torque threshold at least until the desired torque remains above the desired torque required torque threshold.

According to one embodiment of the present disclosure, wherein increasing the engine output is initiated in response to the requested wheel torque exceeding the sum of a maximum available electric machine torque and a maximum available engine torque.

According to one embodiment of the present disclosure, wherein increasing the engine output is initiated in response to the vehicle speed being below a wheel speed threshold when the ring gear torque is below a ring gear torque threshold.

In accordance with the present disclosure, there is provided a vehicle comprising: an engine; a planetary gear set coupled to the engine and having a ring gear transmitting ring gear torque to a differential; an electric machine configured to selectively output torque to the differential ; Continuous Torque Transfer Component (CTTM) operatively coupling the ring gear and electric machine to the differential; a controller configured to increase engine output to maintain ring gear torque above a ring gear torque threshold, thereby reducing torque Pass to differential via CTTM

According to one embodiment of the present disclosure, wherein the vehicle further includes an active component coupled to the continuous torque transmitting component to provide torque to the torque transmitting component, the active component having a central shaft, either end of which is operatively Combined to the ring gear and motor.

According to an embodiment of the present disclosure, wherein the controller is further configured to increase the engine output based on the vehicle speed being below a vehicle speed threshold.

According to one embodiment of the present disclosure, wherein the controller is further configured to maintain the engine output above the engine output threshold such that the torque transmitted through the ring gear remains above the ring gear torque threshold at least until the vehicle speed remains below the vehicle speed speed threshold.

According to one embodiment of the present disclosure, wherein the controller is further configured to increase the engine output based on the wheel torque being below a wheel torque threshold.

According to one embodiment of the present disclosure, wherein the controller is further configured to increase the ring gear torque above the ring gear torque threshold in response to the vehicle speed being below the vehicle speed threshold and the wheel torque being below the wheel torque threshold.

Description of drawings

FIG. 1 is a schematic diagram of a power-split hybrid electric vehicle according to one embodiment of the present disclosure.

2A and 2B are graphical representations of programmed engine speed and programmed engine torque versus desired engine power.

3 is a flow diagram of a control strategy implemented by at least one controller that controls engine output to deliver sufficient ring gear torque, according to one embodiment.

4 is another flow diagram of a control strategy implemented by at least one controller that controls engine output to deliver sufficient ring gear torque, according to one embodiment.

Detailed ways

Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and that other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As will be understood by those of ordinary skill in the art, various features shown and described with reference to any one figure may be combined with features shown in one or more other figures to produce features not explicitly shown or described. Example. The combinations of features shown provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of this disclosure are desired for particular applications or implementations.

Referring to FIG. 1 , a hybrid electric vehicle (HEV) 10 includes a power split powertrain. The components of the power splitting described below may be the flow paths of mechanical power or electrical power to the wheels, or the power flow paths of both mechanical power and electrical power to the wheels. A vehicle system controller (VSC) and/or a powertrain control module (PCM) 12 includes a processor and one or more controllers in a network of controllers configured to control various components in the powertrain. These controllers may be broadly referred to as one or more "controllers". Among other components, the controller 12 controls the electric traction battery 14 . The battery 14 has a bi-directional electrical connection so that the battery 14 receives and stores electrical energy (eg, during regenerative braking) and also supplies energy to the electric traction motor 16 (or motor/generator, M/G ₁ ) for propulsion. The controller 12 also controls the operation of an internal combustion engine (ICE) 18 . Both the traction motor 16 and the engine 18 are capable of driving a transmission 20 that ultimately transfers torque to the wheels of the vehicle.

It should be understood that reference to "motor" 16 and "generator" 32 is for convenience and distinction. However, "motor" 16 or "generator" 32 or both "motor" 16 and "generator" 32 may generally be referred to as an "electric machine" or a motor/generator (M/G). Both the motor 16 and the generator 32 can act as motors by providing torque to the driveline, and can act as generators by converting mechanical energy into electrical energy.

The engine 18 transmits power to a torque input shaft 22 connected to the planetary gear set 24 . A one-way clutch (not shown) may be provided along the input shaft 22 to selectively connect the engine 18 to the planetary gear set 24 . The input shaft 22 provides power to a planetary gear set 24 including a ring gear 26 , a sun gear 28 and a planet carrier assembly 30 . More specifically, the input shaft 22 is drivably connected to the planet carrier assembly 30 to provide power to the remainder of the planetary gear set 24 .

A generator 32 (M/G ₂ ) is drivably connected to the sun gear 28 of the planetary gear set 24 . The generator 32 is engageable with the sun gear 28 such that the generator 32 may or may not rotate with the sun gear 28 . When the one-way clutch couples the engine 18 to the planetary gear set 24 , the generator 32 may act as a reactionary element to generate energy that is reactive to the operation of the planetary gear set 24 . The electrical energy generated by the generator 32 is transferred through the electrical connection 36 to the battery 14 where the electrical energy is stored for later use (eg, to propel the vehicle or drive auxiliary components). The battery 14 may also receive and store electrical energy through regenerative braking in a known manner.

The battery 14, motor 16, and generator 32 are all interconnected by electrical connections 36 in a bidirectional electrical flow path such that each component is electrically connected for propulsion and regeneration. In one propulsion mode, the battery 14 supplies stored electrical energy to the motor 16 such that the motor 16 turns downstream components of the drivetrain (described below). The engine 18 may also propel the vehicle by supplying a portion of the power to a generator 32 that can transfer electrical energy to the battery or directly to the motor 16 . In another propulsion mode, the engine 18 provides power to the planetary gear set 24 causing the ring gear 26 to transfer torque to downstream components of the driveline (described below). During this mode, the generator 32 may be disengaged from the planetary gear set 24 so that the generator 32 does not generate power (eg, when the battery has a high state of charge). If selective separation of the generator 32 is not provided, the generator 32 may provide reactive or negative torque when the battery 14 state of charge is high.

The continuous torque transmitting component 40 transmits torque output from either the engine 18 or the motor 16 or both the engine 18 and the motor 16 . The continuous torque transmitting member 40 may be a chain, belt, or other mechanical ring having an input (active) region and an output (driven) region. The continuous torque transmitting component 40 mechanically couples the output of the engine 18 and/or the motor 16 to the differential 42 . More specifically, both the ring gear 26 and the motor 16 provide mechanical output to a shaft 44 extending through a drive member 46 such as a sprocket or the like. Active member 46 may be positioned between ring gear 26 and motor 16 such that active member 46 receives torque from either side. Alternatively, the motor 16 may be placed on the same side of the drive member 46 as the ring gear 26 . The driving member 46 drives the driven member 48 (eg, another sprocket) through mechanical coupling with the continuous torque transmitting member 40 . Coupled to the continuous torque transmitting member 40 at the opposite end away from the shaft 44 is a differential that receives torque and distributes the torque to and between the wheels 52 of the vehicle.

In view of the power-split hybrid described above, it should be clear that the powertrain has two power sources. The first power source is the engine 18 , which transmits torque to the planetary gear set 24 . Other power sources relate only to the electric drive system, which includes the motor 16 , the generator 32 and the battery 14 , where the battery 14 acts as an energy storage medium for the generator 32 and the motor 16 . The generator 32 may be driven by the planetary gear set 24 or may transmit power to the planetary gear set 24 as a motor.

It should be understood that the power split vehicle in FIG. 1 is merely an example, and that the present disclosure is not meant to be limited to this arrangement. Other power-split vehicles are contemplated within the scope of the control strategy of the present disclosure. It should be understood, however, that in all embodiments, a continuous torque transmitting member (instead of a torque reduction gear set) is provided to transmit torque from the torque generating elements to the wheels.

When one or both power sources operate to provide torque to the wheels, the torque is transmitted through the continuous torque transmitting member 40 . The combined torque ultimately delivered to the wheels is the sum of the torque provided by motor 16 (motor torque) and the torque provided by ring gear 26 (ring gear torque), as shown in equation (1) below:

T _wheel =T _ring +T _motor (1)

The amount of ring gear torque depends on the reactive torque provided by the generator 32, which in turn depends on the amount of change in engine torque and commanded engine speed. It can be seen that the maximum available wheel torque occurs when both the motor 16 and the engine 18 are delivering full torque.

The desired engine power is planned based on equation (2) below:

P _{eng_des} =P _{wheel_des} +P _losses +P _accessory -P _battery (2)

where P _{wheel_des} is the desired wheel power, P _losses is the expected power loss, P _accessory is the electrical accessory load (eg, HVAC, radio, etc.), and P _battery is the battery charge for state of charge (SOC) management or Desired level of discharge.

Given a desired engine power, engine speed and torque are planned through a map designed to deliver the planned engine speed and torque at an efficient engine speed set point. FIG. 2A shows a predetermined engine speed map, and FIG. 2B shows a planned engine torque map selected during operation given the above criteria. (Figure 2B also includes the minimum engine torque limit and minimum engine power lines described further below.)

Especially at low vehicle speeds, situations may arise where the amount of wheel power is relatively small and the wheel torque demand is relatively large. Such a situation arises, for example, when the operator of the vehicle needs to fully accelerate quickly (depress the accelerator pedal fully) when the vehicle is stopped. At the beginning of the acceleration demand, the wheel speed is zero, and thus the wheel power is also zero, but the wheel torque demand is at a maximum. Another similar situation may arise where the vehicle operator presses the accelerator pedal sharply when the vehicle is running at low or zero speed on sand or gravel. According to various embodiments of the present disclosure, the controller 12 is configured to maximize the wheel torque delivered under these conditions described above.

Assuming that the requested wheel torque is at least as large as the sum of the maximum available motor torque and the maximum available engine torque when the accelerator pedal is fully depressed, the control strategy presented here will ensure that the wheel torque is maximum at full accelerator pedal depression . The control strategy will also ensure that the requested wheel power is available under partial pedaling operation. An example of an algorithm used and implemented by the controller 12 is shown and described with reference to FIGS. 3 and 4 .

3 and 4 are diagrams illustrating the operation of a system or method for controlling a vehicle according to an embodiment of the present disclosure. As will be understood by one of ordinary skill in the art, the operations or functions represented in FIGS. 3 and 4 may be performed by software and/or hardware depending on the particular application or implementation. Various operations or functions may be performed in an order or sequence other than that explicitly shown or described, which may depend upon a particular process strategy (eg, event-driven, interrupt-driven, etc.). Likewise, one or more operations, tasks or functions may be repeatedly performed, performed in parallel, and/or omitted under particular operating conditions or in particular applications, although not explicitly shown. In one embodiment, the illustrated operations may be implemented primarily by software, instructions or code stored in non-transitory computer-readable storage and executed by one or more microprocessor-based computers or Executed by a controller for controlling the operation of associated vehicle components.

Referring to FIG. 3 , for example, an exemplary algorithm 100 begins at 102 in response to, for example, a high torque demand at low vehicle speed and low wheel power (as explained above). First, at 104, a minimum engine torque output limit (T _{engine_min} ) is determined. The minimum engine torque output limit ensures that the torque output by the engine is sufficient to meet the required wheel torque. Using the maximum motor torque limit (T _{motor_max} ), and assuming constant engine speed, for a given wheel torque demand, the engine torque should exceed the product of the transmission ratio and the difference between the wheel torque and the motor torque limit, as shown by the following relationship :

T _{engine_min ≥gear} ratio*(T _wheel -T _{motor_max} ) (3)

Therein, if gears are provided, the gear ratio is a function of the difference between the driving member 46 and the driven member 48 . Of course, other mechanisms can be used that provide the speed change between the shaft 44 and the differential input that should be calculated in equation (3). If there is no transmission differential between the driving member 46 and the driven member 48 and the continuous torque transmitting member transmits torque in a 1:1 transmission ratio, the term transmission differential can be dropped. In this case, the minimum engine torque output limit corresponds directly to the difference between the wheel torque and the maximum motor torque limit.

At 106 , with the determined minimum engine torque, the minimum engine power (P _min ) can be determined using the map in FIG. 2B . Minimum engine power represents the minimum amount of power required to meet wheel torque demands during a desired acceleration event.

At 108, a maximum limit of engine power (P _{engine_max} ) to prevent battery overcharging is determined. This value represents the maximum amount of engine power that is allowed to be delivered by the engine while taking into account the maximum charge rate the battery can accept. The maximum engine power to prevent battery overcharging can be calculated and set to a limit using the following equation (4):

P _{engine_max} =P _{wheel_des} -P _{battery_charge_limit} +P _losses +P _accessory (4)

where P _{battery_charge_limit} is the maximum charge power limit at which the battery can accept charging at the maximum rate, which may be limited by the design of the battery connector and battery chemistry.

The controller sets the maximum power limit, generally represented by blocks 110-114. If the minimum engine power required to meet the wheel torque demand is greater than the maximum available engine power (considering SOC overcharge protection), then increase the minimum power from the ring gear and through the ring gear to the continuous torque transmitting components to at least the maximum Available engine power. More specifically, at 110, a comparison is made between _Pmin and _{Pengine_max} . If the minimum engine power (P _min ) is less than the maximum engine power limit (P _{engine_max} ), then at 112 the controller sets the minimum ring gear power threshold (P _{min —ring} ) to the determined minimum engine power (P _min ). However, if the minimum engine power (P _min ) exceeds the maximum limit of engine power (P _{engine_max} ), then at 114 the controller sets the threshold P _{min_ring} equal to the maximum limit of engine power (P _{engine_max} ).

At 116 , the desired engine power (P _eng — des ) is determined using equation (2) above.

In view of the above description, it should be understood that if the desired engine power determined by the wheel power demand is less than the minimum engine power required to satisfy the wheel torque, the controller can increase the engine power demand to this value. This ultimately increases the power transferred from the ring gear. However, if the desired engine power determined by the wheel power demand has exceeded the minimum engine power required to meet the wheel torque, such action is not required and the engine power demand can be maintained.

Given the above parameters, an engine power command can then be determined to enable the engine to output power to meet the torque demand at the wheels, particularly under the low speed, high torque demand conditions described above. At 118, a comparison is made between the desired engine power ( _{Peng_des} ) and the minimum ring gear power threshold ( _Pmin-ring ) (determined at 110-114). If the desired engine power exceeds the minimum ring gear power, then at 120 the controller sets the engine power command to the desired engine power (P _eng — des ). However, if the minimum ring gear power exceeds the desired engine power, the controller sets the engine power command to the minimum ring gear power at 122 . At 124, the algorithm ends and can return.

Steps 118-122 manage engine power settings and are commanded by the controller such that the power output by the ring gear exceeds a threshold to provide the desired torque to the wheels.

FIG. 4 illustrates a simplified, higher-level control strategy or algorithm 200 that provides desired wheel torque according to an embodiment of the present disclosure. At 202 , a minimum engine power output to meet the wheel torque demand is determined. At 204 , the current maximum available engine output is determined, similar to that shown at step 108 . At 206, a minimum ring gear torque threshold is determined in a similar manner as described with reference to blocks 110-114. In particular, the minimum ring gear torque threshold corresponds to the lesser of the minimum engine power required to meet the wheel torque demand and the maximum available engine power. At 208 , the controller modifies the engine output such that the ring gear torque exceeds the minimum ring gear torque threshold.

The various embodiments of the present disclosure described above provide strategies for varying engine output (power) to deliver ring gear torque that satisfies the torque required at the wheels. Briefly, the control strategy determines and corrects the engine power request such that the resulting ring gear torque exceeds an associated threshold. The ring gear threshold may be determined using the engine torque limit and the requested wheel torque (details above). In some embodiments, a minimum engine power request is determined and provided such that sufficient engine torque will be programmed to deliver the minimum ring gear torque. This minimum amount of engine power provides the desired wheel torque while considering engine efficiency. In some embodiments, the maximum engine power output may be determined based on the wheel power request and the battery charge limit.

When the engine output is varied to ensure that the torque transmitted by the ring gear is above the ring gear torque threshold, torque is transmitted through the continuous torque transmitting components and to the wheels to meet the desired and desired wheel torque.

It should be understood that references to "torque" and "power" above (such as a minimum ring gear power threshold) may be interchanged by a simple mathematical relationship between torque and power (power=torque*speed). Therefore, the minimum ring gear power threshold may also be the minimum ring gear torque threshold by simply dividing by the rotational speed. The present disclosure should not be limited by a strict "power" threshold or a strict "torque" threshold. An example of such a transition may be made between steps 104 and 106 . According to embodiments of the present disclosure, engine power is modified to provide the desired torque to the wheels.

The processes, methods, or algorithms disclosed herein can be delivered to, or executed by, a processing device, controller, or computer, which can include any existing programmable electronic control unit or dedicated electronic control unit. accomplish. Likewise, the processes, methods or algorithms may be stored as executable data or instructions by a controller or computer in a variety of forms including, but not limited to, permanent storage on a non-writable storage medium (such as a read-only storage medium). memory device) or information that is changeably stored on a writable storage medium such as a floppy disk, magnetic tape, CD, random access memory, or other magnetic and optical media. The processes, methods or algorithms can also be implemented in software executable objects. Alternatively, the processes, methods or algorithms may also employ, in whole or in part, suitable hardware components such as application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), state machines, controllers or other hardware components or device, or a combination of hardware, software and firmware components).

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments may be combined to form further embodiments of the invention not expressly shown or described. Although various embodiments may have been described as providing advantages or advantages over other embodiments or prior art implementations with respect to one or more desirable characteristics, those of ordinary skill in the art will recognize that depending on the particular application and implementation In this way, one or more features can be compromised to achieve desired overall system properties. These attributes may include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, and the like. Accordingly, embodiments described as inferior to other embodiments or prior art implementations in one or more characteristics are not outside the scope of this disclosure and may be desired for a particular application.

Claims (7)

1. A vehicle, comprising:

an engine;

a planetary gear set coupled to the engine and having a ring gear that transfers ring gear torque to the differential;

a motor configured to selectively output torque to the differential;

a continuous torque transmitting member operatively coupling the ring gear and the electric machine to the differential;

a controller configured to vary an engine output based on a ring gear torque threshold to thereby transfer a desired torque through the continuous torque transmitting member to the differential,

wherein the ring gear torque threshold is determined by comparing a minimum engine power determined based on the wheel torque request and a maximum motor torque limit and a maximum available engine power.

2. The vehicle of claim 1, further comprising a first sprocket and a second sprocket, the continuous torque transmitting member extending around the first sprocket and the second sprocket, the continuous torque transmitting member operably coupling the ring gear and the motor at the first sprocket to the differential at the second sprocket, wherein the first sprocket is a drive member coupled to the continuous torque transmitting member to provide torque to the continuous torque transmitting member, the drive member having a central shaft with a first end operably coupled to the ring gear and a second end operably coupled to the motor.

3. The vehicle according to claim 1, wherein the controller is configured to vary the engine output based on the motor output torque approaching a maximum amount or a maximum amount.

4. The vehicle of claim 1, wherein the controller is configured to vary the engine output further based on the requested wheel torque exceeding a sum of a maximum available motor torque and a maximum available engine torque.

5. The vehicle of claim 1, wherein the controller is further configured to increase engine output based on the wheel torque being below a wheel torque threshold.

6. The vehicle of claim 1, wherein the controller is further configured to increase the ring gear torque above the ring gear torque threshold in response to the vehicle speed being below a vehicle speed threshold and the wheel torque being below a wheel torque threshold.

7. The vehicle of claim 1, wherein a minimum ring gear torque threshold corresponds to the lesser of the minimum engine power and the maximum available engine power.

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